Postretirement Benefit Plans (Summary of Amounts Recognized in Financial Statements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in benefit obligation:
Benefit obligation at beginning of year	$ 1,008
Benefit obligation at end of year	1,199	$ 1,008
Change in plan assets:
Beginning Balance	605
Ending Balance	691	605
Unfunded status of the plans	(508)	(403)
United States
Change in benefit obligation:
Benefit obligation at beginning of year	113	99
Service cost	3	3	$ 3
Interest cost	3	4	4
Benefits paid	(6)	(7)
Actuarial loss (gain)	10	15
Plan amendments, settlements and curtailments	0	0
Foreign currency translation/other	0	(1)
Benefit obligation at end of year	123	113	99
Change in plan assets:
Beginning Balance	105	97
Employer contributions	0	0
Actual return on plan assets	14	17
Benefits paid	(6)	(7)
Plan amendments, settlements and curtailments	0	0
Foreign currency translation/other	0	(2)
Ending Balance	113	105	97
Unfunded status of the plans	(10)	(8)
International defined benefit pension plans
Change in benefit obligation:
Benefit obligation at beginning of year	846	763
Service cost	13	9	9
Interest cost	16	19	19
Benefits paid	(34)	(28)
Actuarial loss (gain)	130	104
Plan amendments, settlements and curtailments	(1)	(23)
Foreign currency translation/other	62	2
Benefit obligation at end of year	1,032	846	763
Change in plan assets:
Beginning Balance	500	470
Employer contributions	24	16
Actual return on plan assets	70	52
Benefits paid	(34)	(28)
Plan amendments, settlements and curtailments	(1)	(23)
Foreign currency translation/other	19	13
Ending Balance	578	500	$ 470
Unfunded status of the plans	$ (454)	$ (346)